PROJECT SUMMARY Background: Worldwide there are estimated to be 2.9 million cholera cases annually. Effective targeted water, sanitation, and hygiene (WASH) interventions are urgently needed to reduce cholera globally. Our study in Bangladesh found that individuals living within 50 meters of a cholera patient were at 30 times higher risk of developing cholera than the general population during the first week after the index patient sought care at a health facility. However, there has been little work done to develop and evaluate interventions for this high risk population. Objective: Our objective is to develop and evaluate the effectiveness of a ring WASH intervention in reducing cholera infections and increasing sustained WASH behaviors in transmission hotspots around cholera cases. Previous studies: Our research group developed the Cholera-Hospital-Based-Intervention-for-7-Days (CHoBI7), a WASH intervention delivered to cholera patients and their household members in a health facility. Our randomized controlled trial (RCT) in Bangladesh of CHoBI7 demonstrated this intervention was effective in significantly reducing cholera, and led to sustained increases in handwashing with soap and improved drinking water quality 12 months post-intervention in cholera patient households. This intervention, however, solely focused on cholera patients households. There are no studies to date that have evaluated the impact on reducing cholera of delivering a ring WASH intervention to households living near cholera patients. Design and Setting: The Director of Disease Control at the Bangladesh Ministry of Health and Family Welfare would like to take CHoBI7 to scale across Bangladesh, and has requested we build evidence on scalable approaches for delivering CHoBI7 in a ring around cholera patient households. This study will have 3 phases. During the formative research and planning phase we will develop a scalable, theory and evidence based ring WASH intervention through in-depth interviews, focus group discussions, workshops, and a pilot. During the intervention implementation and evaluation phase we will conduct a RCT to prospectively follow 3120 participants from 1040 households living in 40 rings around cholera cases to evaluate the effectiveness of the intervention in: (1) reducing cholera infections during the first week after the index patient in the ring seeks care at a health facility; and (2) increasing handwashing with soap and stored water quality over a 12 month period. The first arm will receive the standard recommendation given in Bangladesh during diarrhea outbreaks on oral rehydration solution use and a leaflet on WASH practices during a single visit. The second arm will receive this message and the ring WASH intervention which includes two home visits and mobile health messages. Whole genome sequencing will be performed on water and clinical Vibrio cholerae strains collected to investigate spatiotemporal transmission dynamics of V. cholerae in hotspots. During the dissemination and policy planning phase, we will partner with the Director of Disease Control to disseminate study findings and inform cholera control policies. Significance: This will be the first RCT of a ring WASH program to reduce cholera.